thanku ...im using ga-ma69vm-s2 mother board ...can i use hd radeon 5570 or 5550 cards ?
Yes but those cards won't give as much value as the 4670. You would be paying for DX11 capability but the cards are too slow to deal with it anyway.
^+1 its right the hd 4670 will be more powerful than the 5570 or 5550 cards...if you want to get the performance like hd 4670 and also dx 11 than save a bit more and get hd 5670 ...it's a way better than all the card mentioned above...
Cards depend on your moniter res higher the res more powerful cards lower the res lesser powered cards